HACKENSACK — Lawyers for former city police chief Ken Zisa plan to argue that his convictions on official misconduct and insurance fraud charges should be voided, NorthJersey.com reports.

Zisa is scheduled to be sentenced on Aug. 30, and is facing at least 23 years in prison. Before then, however, his team of lawyers will attempt to convince a Superior Court judge that his May convictions were the result of a flawed trial.

According to The Record, their contentions include that the convictions were based on insufficient evidence, that investigators in the prosecutor's office destroyed evidence that worked in Zisa's favor, and that officers who testified against him were granted improper immunity agreements.

A hearing on their arguments has been scheduled for Aug. 21. The prosecutor's office will also be allowed to defend its case and the convictions.

Zisa served as Hackensack's police chief for 15 years, and as a state assemblyman for eight.

A jury convicted him in May after prosecutors argued that Zisa interfered with a pair of investigations involving his girlfriend Kathleen Tiernan's sons in 2004 and 2008, and that he had helped to cover up a 2008 accident during which Tiernan was allegedly driving drunk.

Zisa was also convicted of filing fraudulent insurance claims related to that accident.